The "dynamic state" hypothesis of viral persistence permits to postulate that, depending on fluctuations of and interaction between the humoral response and virus replication, a herpetic recurrence may either be elicited or aborted. To test this, a long-term experiment will be instituted in ocularly infected rabbits. The serum antibody and virus replication in the eyes will be measured at close intervals and viral and clinical recurrences recorded. It is hypothesized that a recurrence may coincide with a transient decrease of the immune response, followed by an increase of virus replication. As recurrences can be induced by systemically applied epinephrine, it can be envisioned that epinephrine, via increased release of ACTH, may elevate serum cortisone levels and, thereby, suppress the immune response. Therefore, continuous titrations of virus and neutralizing antibody will be parallelled by serum cortisone measurements, WBC counts and differentials. Passively administered antibody significantly ameliorates the herpetic eye disease, most probably due to its virus- neutralizing action. Therefore, homologous immune serum will be injected at regular time intervals into infected rabbits to see whether a sustained high level of antibody may reduce the frequency and/or severity of recurrences. Virus strains obtained from successive recurrences as well as recent human eye isolates of HSV will be tested for a broad array of biological properties, such as antigenic composition, pathogenicity, sensitivity to antiviral substances, CPE- and plaque type.